Contribution of x-ray incident position dependence to energy resolution of Ti/Au transition-edge sensors

We present the contribution of x-ray incident-position dependence on the absorber to the energy resolution of Ti/Au transition-edge sensors (TESs). The pulse height varies with the position due to insufficient thermal conductivity and geometry of the absorber that degrades the measured energy resolution. We develop a three-dimensional (3D) electro-thermal simulation model and thoroughly study the position dependent contribution to energy resolution (ΔE_p) for two presentative absorber structures: an absorber directly deposited on the center of TES sensor (design A) and an absorber cantilevered on the TES sensor by several stems (design B). For design A with a 30 μm × 40 μm Au absorber ΔE_p is found to be 9.4 eV, while it is reduced to 1.35 eV for design B with a 100 μm × 100 μm Au absorber. Although the contribution of position dependence is relatively small, this study facilitates further optimization of the absorber structure to achieve enhanced energy resolution.